#include<netinet/in.h> // sockaddr_in 
#include<sys/types.h>  // socket 
#include<sys/socket.h> // socket 
#include<stdio.h>    // printf 
#include<stdlib.h>   // exit 
#include<string.h>   // bzero 
  
#define SERVER_PORT 8000 
#define LENGTH_OF_LISTEN_QUEUE 20 
#define BUFFER_SIZE 1024 
#define FILE_NAME_MAX_SIZE 512 
  
int main(void) 
{ 
  // 声明并初始化一个服务器端的socket地址结构 
  struct sockaddr_in server_addr; 
  bzero(&server_addr, sizeof(server_addr)); 
  server_addr.sin_family = AF_INET; 
  server_addr.sin_addr.s_addr = htons(INADDR_ANY); 
  server_addr.sin_port = htons(SERVER_PORT); 
  
  // 创建socket，若成功，返回socket描述符 
  int server_socket_fd = socket(PF_INET, SOCK_STREAM, 0); 
  if(server_socket_fd < 0) 
  { 
    perror("Create Socket Failed:"); 
    exit(1); 
  } 
  int opt = 1; 
  setsockopt(server_socket_fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt)); 
  
  // 绑定socket和socket地址结构 
  if(-1 == (bind(server_socket_fd, (struct sockaddr*)&server_addr, sizeof(server_addr)))) 
  { 
    perror("Server Bind Failed:"); 
    exit(1); 
  } 
    
  // socket监听 
  if(-1 == (listen(server_socket_fd, LENGTH_OF_LISTEN_QUEUE))) 
  { 
    perror("Server Listen Failed:"); 
    exit(1); 
  } 
  
  while(1) 
  { 
    // 定义客户端的socket地址结构 
    struct sockaddr_in client_addr; 
    socklen_t client_addr_length = sizeof(client_addr); 
  
    // 接受连接请求，返回一个新的socket(描述符)，这个新socket用于同连接的客户端通信 
    // accept函数会把连接到的客户端信息写到client_addr中 
    int new_server_socket_fd = accept(server_socket_fd, (struct sockaddr*)&client_addr, &client_addr_length); 
    if(new_server_socket_fd < 0) 
    { 
      perror("Server Accept Failed:"); 
      break; 
    } 
  
    // recv函数接收数据到缓冲区buffer中 
    char buffer[BUFFER_SIZE]; 
    bzero(buffer, BUFFER_SIZE); 
    if(recv(new_server_socket_fd, buffer, BUFFER_SIZE, 0) < 0) 
    { 
      perror("Server Recieve Data Failed:"); 
      break; 
    } 
  
    // 然后从buffer(缓冲区)拷贝到file_name中 
    char file_name[FILE_NAME_MAX_SIZE+1]; 
    bzero(file_name, FILE_NAME_MAX_SIZE+1); 
    strncpy(file_name, buffer, strlen(buffer)>FILE_NAME_MAX_SIZE?FILE_NAME_MAX_SIZE:strlen(buffer)); 
    printf("%s\n", file_name); 
  
    // 打开文件并读取文件数据 
    FILE *fp = fopen(file_name, "r"); 
    if(NULL == fp) 
    { 
      printf("File:%s Not Found\n", file_name); 
    } 
    else
    { 
      bzero(buffer, BUFFER_SIZE); 
      int length = 0; 
      // 每读取一段数据，便将其发送给客户端，循环直到文件读完为止 
      while((length = fread(buffer, sizeof(char), BUFFER_SIZE, fp)) > 0) 
      { 
        if(send(new_server_socket_fd, buffer, length, 0) < 0) 
        { 
          printf("Send File:%s Failed./n", file_name); 
          break; 
        } 
        bzero(buffer, BUFFER_SIZE); 
      } 
  
      // 关闭文件 
      fclose(fp); 
      printf("File:%s Transfer Successful!\n", file_name); 
    } 
    // 关闭与客户端的连接 
    close(new_server_socket_fd); 
  } 
  // 关闭监听用的socket 
  close(server_socket_fd); 
  return 0; 
} 

